Erosion-Resistant Multilateral Junctions

ABSTRACT

A lateral junction for a multilateral wellbore having a main bore and a lateral leg which extends away from the main bore. The lateral junction includes a seal bore diverter and a hanger that is insertable into the seal bore diverter to form the junction. An engagement mechanism interlocks the hanger and seal bore diverter together at the crux of their joining.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to the design of multi-lateral junctions used in downhole hydrocarbon production and methods for creating such junctions in a wellbore.

2. Description of the Related Art

Multilateral wellbores are used to increase the efficiency of drilling and production. A multilateral wellbore includes a main wellbore, which is drilled from the surface, and at least one lateral leg which branches out from the main wellbore. The main wellbore, or at least a portion thereof, is typically vertical or substantially vertical in orientation. The lateral leg(s) usually have a horizontal or deviated orientation with respect to the main wellbore and may be capable of accessing hydrocarbons that are not accessible from the main wellbore.

A downhole junction is used to branch a lateral leg from a central, usually substantially vertical main wellbore. Current mechanical junction arrangements allow formation exposure gaps to develop which increase the risk of erosion and possible intrusion of debris at the junction itself.

SUMMARY OF THE INVENTION

The present invention provides devices and methods for providing multilateral junctions in a wellbore. In a described embodiment, a lateral junction is provided by a hanger and a seal bore diverter (SBD). The SBD includes a tubular body with an elongated window formed within. In preferred embodiments, the lower end of the elongated window includes an engagement hook. The hanger includes a straight portion and a deviated portion which can pass through the elongated window of the SBD. It is noted that while the deviated portion will be depicted herein as deviating from, and actually will deviate from the axis of the straight portion when installed in the wellbore, the hanger will typically be a substantially straight tubular when manufactured and run into the wellbore. The hanger also features lateral windows formed in its body as well as an engagement tab. In accordance with preferred embodiments, an orientation mechanism is provided which angularly orients the hanger within the SBD.

In operation to create a lined lateral junction in a multilateral wellbore, a SBD is first landed within the main bore of a multilateral wellbore, oriented so that its elongated window faces a lateral leg which diverges from the main bore. Thereafter, a hanger is lowered into the main bore so that the deviated portion of the hanger enters the central bore of the SBD. If an orientation mechanism is provided, the hanger is then angularly oriented within the SBD so that the deviated portion of the hanger will be pointed toward and exit through the elongated window of the SBD.

When the hanger is fully seated within the SBD, an engagement hook on the SBD will become interlocked with an engagement tab on the hanger. The interlocking engagement will preferably occur at the crux of the acute angular junction where the hanger and SBD meet. The interlocking engagement is formed at the interior portion of the junction between the hanger and SBD. The completed assembly provides a lined junction within which completions or other tools can be run.

BRIEF DESCRIPTION OF THE DRAWINGS

For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, wherein like reference numerals designate like or similar elements throughout the several figures of the drawings and wherein:

FIG. 1 is a side, cross-sectional view of an exemplary wellbore having a main bore and a single lateral leg and a seal bore diverter landed within.

FIG. 2 is a side, cross-sectional view of the wellbore shown in FIG. 1 with a hanger now landed within the seal bore diverter.

FIG. 3 is an external isometric view of an exemplary hanger being run into an exemplary seal bore diverter.

FIG. 4 is an external isometric view of the hanger and seal bore diverter of FIG. 3, now with the hanger having been angularly oriented within the seal bore diverter.

FIG. 5 is an external isometric view of the hanger and seal bore diverter shown in FIG. 3, now with the hanger having been fully landed within the seal bore diverter.

FIG. 6 is a side, cross-sectional view of a hanger landed within a seal bore diverter.

FIG. 7 is an isometric view of an axial cross-section of a hanger landed within a seal bore diverter to illustrate an exemplary engagement hook in greater detail.

FIG. 8 is an external view of an exemplary hanger illustrating exemplary lateral window placement.

FIG. 9 is an external view of an exemplary seal bore diverter illustrating an exemplary design for an elongated window formed therein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The term “multilateral,” as used herein, will refer to wellbores having a main bore, or leg, and at least one lateral leg which branches off from the main bore. FIG. 1 illustrates an exemplary multilateral wellbore 10 that has been drilled through the earth 12 from the surface (not shown). The depicted wellbore 10 includes a main bore, or main leg 14. The main bore 14 has been lined with metallic casing 16 and cement 18, as is known in the art. A casing window 20 has been previously milled through the casing 16 and cement 18 and a lateral leg 22 has been drilled which extends outwardly from the main bore 14. A metallic liner 24 has been secured within the main bore 14 below the casing window 20 with packer 26.

In FIG. 1, a seal bore diverter (SBD) 28 has been run into the wellbore 10 and its lower end 30 is landed within the liner 24. The SBD 28 has a tubular body 32 which defines a central bore 34 along its length. An elongated window 36 is formed in the body 32. A SBD 28 is illustrated in FIG. 9 showing an exemplary elongated window 36.

When the SBD 28 is landed in the liner 24, the elongated window 36 is oriented to face the casing window 20.

An interior ramp shoulder 38 is formed within the central bore 34 of the SBD 28. The ramp shoulder 38 is formed by thickening the body 32 of the SBD 28 to form the ramp shoulder 38, as best appreciated by reference to FIG. 6. Upper end surface 40 of the SBD 28 is angled to serve as a mechanism for orienting a hanger within the SBD 28, as will be described. An engagement hook 42 is located at the lower end of the elongated window 36.

As shown in FIGS. 2-6 a hanger 44 is then landed within the SBD 28 in order to form an erosion-resistant lateral junction 45. The hanger 44 includes a straight portion 46 and a deviated portion 48. It is noted that, in FIGS. 1-6, the angle of departure between the deviated portion 48 of the hanger 44 and the straight portion 46 is exaggerated for the purposes of better illustrating the invention. The deviated portion 48 should depart from the axis of the straight portion 46 at an angle that generally matches the angle at which the lateral leg 22 departs from the main bore 18. The hanger 44 has a generally tubular body 50 which defines a central bore 52 along its length. It is noted that the elongated window 36 of the SBD 28 should be wide enough to permit the deviated portion 48 of the hanger 44 to pass through. Preferably, an outer orientation sleeve 54 surrounds an upper portion of the straight portion 46 of the hanger 44. The orientation sleeve 54 presents an angled lower shoulder 55 which is complementary to the angled upper end 40 of the SBD 28.

A first lateral window 56 is formed in the body 50 of the hanger 44 in the vicinity of the elbow 58 which joins the straight portion 46 to the deviated portion 48. A second, smaller lateral window 60 is also formed in the body 50 adjacent the lateral window 56, and an engagement tab 62 is formed between the two lateral windows 56, 60. FIG. 8 more clearly depicts the appearance of exemplary lateral windows 56, 60 as well as an engagement tab 62 for a hanger 44. The second window 60 allows the creation of the engagement tab 62, but the lowermost taper of the second window 60 allows that window 60 to fit the outer diameter of the SBD tubular body 32. A close fit is important for minimizing erosion.

In order to land the hanger 44 within the SBD 28, the deviated portion 48 is slid into the central bore 34 of the SBD 28, as illustrated by FIG. 3, in the direction of arrow 64. When the hanger 44 is moved to the position shown in FIG. 4, the lower shoulder 55 of the orientation sleeve 54 of the hanger 44 will contact the angled upper end surface 40 of the SBD 28 and angularly orient the hanger 44 within so that the deviated portion 48 is directed out of the elongated window 36 of the SBD 28 and the lateral window 56 of the hanger 44 is oriented toward the ramp shoulder 38 of the SBD 28. Thus, the orientation sleeve 54 and upper end surface 40 act as an orientation mechanism for orienting the hanger 44 with respect to the SBD 28.

The hanger 44 continues to slide in the direction of arrow 64 until it is in the fully landed position depicted in FIG. 5. In this fully landed position, a raised shoulder 66 on the outer surface of the hanger 44 will contact and shoulder out against the upper end of the orientation sleeve 54 so that further downward movement of the hanger 44 with respect to the SBD 28 is stopped. If desired, collets 68 on the straight portion 46 of the hanger 44 will snap into a complementary profile (not shown) in the SBD 28 to help lock the hanger 44 and the SBD 28 together.

Also in the fully landed position, the engagement hook 42 of the SBD 28 and the engagement tab 62 of the hanger 44 will interlock. As best shown in FIGS. 6 and 7, the engagement hook 42 of the SBD 28 slides into the smaller lateral window 60 of the hanger 44. The engagement tab 62 of the hanger 44 will be caught beneath the engagement hook 42. This interlocking will stabilize the lateral junction created between the hanger 44 and SBD 28 and will prevent or limit bifurcation between the hanger 44 and SBD 28 at the point where the lateral leg 22 departs from the main bore 14, thereby preventing the later creation of formation exposure gaps (i.e., gaps between the hanger 44 and SBD 28) which increase the risk of erosion and possible intrusion of debris at the junction itself. The interlock of the engagement hook 42 and the engagement tab 62 is located at the crux 70 (in FIG. 2) of the junction between the deviated portion 48 of the hanger 44 and the central bore 34 of the SBD 28.

It is preferable to design the SBD window 36 and the central bore 34 of the SBD 28 to closely match the outer diameter of the hanger 44 at a predetermined angle and deviation to minimize any potential exposure gaps. In addition to the close fit, the SBD 28 and hanger 44 are anchored relative to each other to preserve designed gaps for the remainder of the life of the well. Because the engagement tab 62 does not protrude from the outer diameter of the hanger body 50, the hanger body 50 can closely match the inner diameter of the central bore 34 and window geometry, thereby keeping formation exposure gaps to a minimum. According to preferred embodiments, the window 36 of the SBD 28 is shaped to fit the hanger body 50 at a specified angle relative to the tubular SBD body 32. This angle, as illustrated by the angle of the deviated portion 48 of the hanger 44, will be similar to the angle at which the casing exit was originally milled. Because the outer diameter of the hanger 44 closely matches the interior diameter of the central bore 34, the maximum window width will be close to the central bore 34 diameter. The upper taper of the SBD window 36 is shaped to fit the outer diameter of the hanger 44 at the predetermined angle or deviation. The lower most portion of the SBD window 36 is for the engagement of the engagement tab 62.

After the hanger 44 is landed within the SBD 28, as described above, a completed junction is provided which is fully lined. A user can insert completions or other tools through the central bore 34 and into the lateral leg 22 of the wellbore 10 through the deviated portion 48 of the hanger 44. In addition, a user can have access to the main bore 14 of the wellbore 10 below the junction 45 in order to run tools.

Those of skill in the art will recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein and that the invention is limited only by the claims that follow and any equivalents thereof. 

What is claimed is:
 1. A lateral junction for a multilateral wellbore having a main bore and a lateral leg which extends away from the main bore, the junction comprising: a seal bore diverter to be inserted into the main bore, the seal bore diverter comprising a generally tubular body defining a central bore along its length; an elongated window formed in the tubular body of the seal bore diverter; a hanger to be landed within the central bore of the seal bore diverter to create the lateral junction, the hanger having a generally tubular body with a straight portion and a deviated portion which is shaped and sized to be disposed through the central bore of the seal bore diverter and exit through the elongated window; and an engagement mechanism to interlock the hanger and seal bore diverter together.
 2. The lateral junction of claim 1 wherein the engagement mechanism comprises: an engagement hook formed within the seal bore diverter and is shaped and sized to interlock with a complementary portion of the hanger.
 3. The lateral junction of claim 1 wherein the engagement mechanism comprises: an engagement tab formed within the hanger and is shaped and sized to interlock with a complimentary portion of the seal bore diverter.
 4. The lateral junction of claim 1 wherein: the seal bore diverter and hanger form a crux when the hanger is landed within the seal bore diverter; and the engagement mechanism interlocks the hanger and seal bore diverter together at the crux.
 5. The lateral junction of claim 3 further comprising: a first lateral window formed within the body of the hanger; a second lateral window formed within the body of the hanger; and the engagement tab being defined between the first and second lateral windows.
 6. A lateral junction of claim 1 further comprising an orientation mechanism for angularly orienting the hanger within the seal bore diverter as the hanger is inserted into the seal bore diverter, the orientation mechanism comprising: an angled upper end surface on the seal bore diverter; an orientation sleeve operably associated with the hanger, the orientation sleeve presenting a lower shoulder that is shaped and sized to be complementary to the angled upper end surface; and wherein the hanger is angularly oriented within the seal bore diverter as the lower shoulder is brought into engaging contact with the angled upper end surface.
 7. A lateral junction for a multilateral wellbore having a main bore and a lateral leg which extends away from the main bore, the junction comprising: a seal bore diverter to be inserted into the main bore, the seal bore diverter comprising a generally tubular body defining a central bore along its length; an elongated window formed in the tubular body of the seal bore diverter; a hanger to be landed within the central bore of the seal bore diverter to create the lateral junction, the hanger having a generally tubular body with a straight portion and a deviated portion which is shaped and sized to be disposed through the central bore of the seal bore diverter and exit through the elongated window; an engagement mechanism to interlock the hanger and seal bore diverter together; the seal bore diverter and hanger form a crux when the hanger is landed within the seal bore diverter; and the engagement mechanism interlocks the hanger and seal bore diverter together at the crux.
 8. The lateral junction of claim 7 wherein the engagement mechanism comprises: an engagement hook formed within the seal bore diverter and is shaped and sized to interlock with a complementary portion of the hanger.
 9. The lateral junction of claim 7 wherein the engagement mechanism comprises: an engagement tab formed within the hanger and is shaped and sized to interlock with a complimentary portion of the seal bore diverter.
 10. The lateral junction of claim 9 further comprising: a first lateral window formed within the body of the hanger; a second lateral window formed within the body of the hanger; and the engagement tab being defined between the first and second lateral windows.
 11. The lateral junction of claim 7 further comprising an orientation mechanism for angularly orienting the hanger within the seal bore diverter as the hanger is inserted into the seal bore diverter, the orientation mechanism comprising: an angled upper end surface on the seal bore diverter; an orientation sleeve operably associated with the hanger, the orientation sleeve presenting a lower shoulder that is shaped and sized to be complementary to the angled upper end surface; and wherein the hanger is angularly oriented within the seal bore diverter as the lower shoulder is brought into engaging contact with the angled upper end surface.
 12. A method of forming a lateral junction within a multilateral wellbore having a main bore and a lateral leg which extends away from the main bore, the method comprising the steps of: disposing a seal bore diverter within the main bore of the wellbore, the seal bore diverter having a generally tubular body defining a central bore along its length and an elongated window formed within the body; inserting a hanger into the central bore of the seal bore diverter, the hanger having a generally tubular body with a straight portion and a deviated portion which is shaped and sized to be disposed through the central bore of the seal bore diverter and exit through the elongated window; causing the deviated portion of the hanger to exit the seal bore diverter through the elongated window, a crux being formed between the deviated portion of the hanger and the body of the seal bore diverter; and forming an interlocking engagement between the hanger and the seal bore diverter at the crux.
 13. The method of claim 12 further comprising the step of angularly orienting the hanger with respect to the seal bore diverter as the hanger is inserted into the central bore of the seal bore diverter.
 14. The method of claim 12 wherein the step of forming an interlocking engagement further comprises engaging an engagement hook formed within the seal bore diverter with an engagement tab formed within the seal bore diverter. 